Ultrasonic diagnostic apparatus, ultrasonic image processing apparatus, ultrasonic image processing program, and ultrasonic image generation method

ABSTRACT

In order to generate a three-dimensional tomographic image in which the visibility of specific tissue that an examiner wants is enhanced, an ultrasonic diagnostic apparatus  100  of the present invention includes: an offset calculating section  16  which increases or decreases the brightness value of each voxel according to the brightness value of each voxel of a three-dimensional tomographic image volume data. The amount of increase or decrease in the brightness value of each voxel of the offset calculating section is adjustable through a control panel  26 , and a tomographic image volume rendering section generates the three-dimensional tomographic image on the basis of a three-dimensional tomographic image volume data in which the brightness value is offset by the offset calculating section.

TECHNICAL FIELD

The present invention relates to an ultrasonic diagnostic apparatus, anultrasonic image processing apparatus, an ultrasonic image processingprogram, and an ultrasonic image generation method and in particular, toa technique of generating a two-dimensional projection image(three-dimensional tomographic image) on the basis of three-dimensionaltomographic image volume data obtained from reflected echo signals ofplural tomographic planes of an object.

BACKGROUND ART

The ultrasonic diagnostic apparatus transmits an ultrasonic wave intothe inside of the object by an ultrasonic probe including pluralultrasonic transducers, receives a reflected echo signal of theultrasonic wave corresponding to the structure of body tissue from theinside of the object, generates a tomographic image, for example, aB-mode image on the basis of the reflected echo signal, and displays theB-mode image for diagnosis.

In such an ultrasonic diagnostic apparatus, generating three-dimensionaltomographic image volume data from reflected echo signals of pluraltomographic planes of the object measured by ultrasonic scanning in ashort-axis direction of the ultrasonic probe and generating an image(three-dimensional tomographic image) by projecting thethree-dimensional tomographic image volume data onto the two-dimensionalprojection plane using a volume rendering technique are known.

The volume rendering technique is to generate a three-dimensionaltomographic image by performing cumulative addition of the brightnessvalues of plural voxels, which are arrayed in the line-of-sightdirection when the three-dimensional tomographic image volume data isviewed from a point on the two-dimensional projection plane, along theline-of-sight direction and setting the result as a pixel value(brightness) of the two-dimensional projection plane while correctingthe brightness values by transparency/opacity of each voxel, forexample.

On the other hand, the brightness of each voxel obtained by ultrasonicscanning is determined according to the acoustic impedance of tissue inthe object, ultrasonic attenuation due to propagation in the object, andthe like. For this reason, it is difficult to generate athree-dimensional tomographic image which characterizes only specifictissues to be diagnosed (for example, with enhanced brightness).

In order to cope with such a problem, for example, a maximum valueprojection method of displaying only high-brightness tissue of thethree-dimensional tomographic image volume data or a minimum valueprojection method of displaying only low-brightness tissue is generallyused. In addition, as disclosed in PTL 1, reversing the brightness levelof a B-mode image so that the three-dimensional structure of a low echoregion can be easily viewed is known.

CITATION LIST

Patent Literature

[PTL 1] JP-A-2008-200441

SUMMARY OF INVENTION Technical Problem

In the conventional technique disclosed in the above Patent Literatureand the like, generating a three-dimensional tomographic image in whichthe visibility of specific tissue that the examiner wants (for example,tissue to be diagnosed) is enhanced is not considered.

That is, since the applications of each one of the maximum valueprojection method, the minimum value projection method, and the methodof reversing the brightness level of a B-mode image are limited, athree-dimensional tomographic image in which the visibility of specifictissue that the examiner wants is enhanced cannot always be freelygenerated. For example, such methods can generate a three-dimensionaltomographic image in which the visibility of high-brightness tissue orlow-brightness tissue is enhanced, but it is difficult to generate athree-dimensional tomographic image in which the visibility of tissuewith medium brightness thereof is enhanced.

Therefore, it is an objective of the present invention to generate athree-dimensional tomographic image in which the visibility of specifictissue that the examiner wants is enhanced.

Solution to Problem

An ultrasonic diagnostic apparatus of the present invention includes: anultrasonic probe which transmits or receives an ultrasonic wave to orfrom an object; a tomographic image volume data generating section whichgenerates three-dimensional tomographic image volume data on the basisof reflected echo signals of plural tomographic planes of the objectmeasured by the ultrasonic probe; a tomographic image volume renderingsection which generates a three-dimensional tomographic image seen fromat least one line-of-sight direction on a two-dimensional projectionplane on the basis of the three-dimensional tomographic image volumedata; a display section which displays the three-dimensional tomographicimage; and an offset calculating section which increases or decreasesthe brightness value of each voxel according to the brightness value ofeach voxel of the three-dimensional tomographic image volume data, andis characterized in that the amount of increase or decrease in thebrightness value of each voxel of the offset calculating section isadjustable through an input interface and the tomographic image volumerendering section generates the three-dimensional tomographic image onthe basis of the three-dimensional tomographic image volume data inwhich the brightness value is offset by the offset calculating section.

According to this, since an examiner can adjust the amount of increaseor decrease in the brightness value of each voxel of the offsetcalculating section through the input interface, it is possible togenerate a three-dimensional tomographic image in which only tissue witha specific brightness value is emphasized. Therefore, it is possible togenerate a three-dimensional tomographic image with enhanced visibilityof desired specific tissue by adjusting the amount of increase in thebrightness value of the desired specific tissue, adjusting the amount ofdecrease in the brightness value of tissue other than the desiredspecific tissue, or adjusting both of them. For example, if the examinerknows the brightness value of desired specific tissue, it is possible toenlarge the amount of increase (offset amount) in the brightness valuecorresponding to the vicinity of the brightness value in advance.Moreover, for example, in the case where it is difficult to see desiredspecific tissue since it is hidden behind high-brightness tissue whenviewing the generated three-dimensional tomographic image, it becomesdifficult for the high-brightness tissue as a wall to be reflected onthe three-dimensional tomographic image if the amount of decrease(offset amount) in the brightness value corresponding to the vicinity ofthe high brightness value is set to be large. As a result, it ispossible to improve the visibility of the desired specific tissue.

In addition, when an elastic image volume data generating section whichgenerates three-dimensional elastic image volume data on the basis ofthe reflected echo signals of the plural tomographic planes of theobject is provided, the offset calculating section may be configured toincrease or decrease the brightness value of each corresponding voxel ofthe three-dimensional tomographic image volume data according to thevalue of elasticity of each voxel of the three-dimensional elastic imagevolume data.

According to this, the examiner can generate a three-dimensionaltomographic image with enhanced visibility of tissue, which has aspecific value of elasticity, on the basis of the value of elasticity(stiffness or softness of tissue) of desired specific tissue. Forexample, if the examiner knows the value of elasticity of desiredspecific tissue, it is possible to enlarge the amount of increase(offset amount) in the brightness value corresponding to the vicinity ofthe value of elasticity in advance. On the other hand, when the examinerwants to observe hard (or soft) tissue, it is possible to find andobserve the hard (or soft) tissue if the amount of increase (offsetamount) in the brightness value corresponding to the high (or low) valueof elasticity is set high.

In addition, the offset calculating section may have plural offsettables in which boundary values for dividing a range of the brightnessvalue of each voxel of the three-dimensional tomographic image volumedata or a range of the value of elasticity of each voxel of thethree-dimensional elastic image volume data into plural regions and theamount of increase or decrease in the brightness value in each of theplural divided regions are set, and the brightness value of each voxelof the three-dimensional tomographic image volume data may be increasedor decreased on the basis of the offset table selected from the pluraloffset tables through the input interface.

For example, plural offset tables, such as an offset table for enhancingthe visibility of tissue with low brightness value, an offset table forenhancing the visibility of tissue with intermediate brightness value,and an offset table for enhancing the visibility of tissue with highbrightness value, may be prepared as default. In this case, since theexaminer only needs to select one of the offset tables, it is good interms of usability. In addition, since the boundary value and the amountof increase or decrease of the offset table can be adjusted through theinput interface, finer adjustment can be performed. As a result, it ispossible to further improve the visibility of tissue that the examinerwants.

In addition, the tomographic image volume rendering section may have anopacity table in which transparency/opacity is set according to thebrightness value of each voxel of the three-dimensional tomographicimage volume data, and the three-dimensional tomographic image may begenerated on the basis of the brightness value of each voxel on a lineof sight in the at least one line-of-sight direction of thethree-dimensional tomographic image volume data and thetransparency/opacity based on the opacity table.

In addition, the tomographic image volume rendering section may have abrightness-opacity map in which transparency/opacity and a color codeare set according to the brightness value of each voxel of thethree-dimensional tomographic image volume data. A two-dimensionaltomographic image may be generated by converting a color of each voxelof tomographic image data of at least one section of thethree-dimensional tomographic image volume data, in which the brightnessvalue is offset, on the basis of the brightness-opacity map, and thedisplay section may display the three-dimensional tomographic image, thetwo-dimensional tomographic image, and the brightness-opacity map.

That is, the transparency/opacity of each voxel becomes an indexindicating how much the voxel is reflected on the three-dimensionaltomographic image. Therefore, by performing color display according tothe transparency/opacity of each voxel of the two-dimensionaltomographic image, the examiner can recognize which part of thetwo-dimensional tomographic image and how much is reflected on thethree-dimensional tomographic image by referring to the two-dimensionaltomographic image. In addition, by referring to the two-dimensionaltomographic image, it becomes easy to perform adjustment of an offsettable for improving the visibility of desired specific tissue. Regardingcolor encoding on a two-dimensional tomographic image based on thetransparency/opacity, when an examiner changes (adjusts) the offsetamount, the position of the brightness boundary, or the gain adjustmentvalue of the tomographic image input value or the opacity table throughthe control panel, that is, when the examiner performs an operation ofcausing a change in opacity processing on the three-dimensionaltomographic image, encoding processing is performed for a fixed time(for example, about 1 to 5 seconds) so that the examiner can see theinfluence of the operation on the three-dimensional tomographic imagethrough the tomographic image. After the elapse of the fixed time (forexample, about 1 to 5 seconds), it is possible to end thetransparency/opacity color encoding and to display a normal tomographicimage so that normal diagnosis can be smoothly performed.

Advantageous Effects of Invention

According to the present invention, it is possible to generate athree-dimensional tomographic image in which the visibility of specifictissue that an examiner wants is enhanced.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram showing the entire configuration of anultrasonic diagnostic apparatus of a first embodiment.

FIG. 2 is a view showing the relationship between the voxel value andthe opacity.

FIG. 3 is a view showing an example of a setting screen of an offsettable used in an offset calculating section.

FIG. 4 is a data flow chart of brightness value conversion processingperformed by the offset calculating section.

FIG. 5 is a schematic view showing a tomographic image of the fetal headexpressed as brightness values of 256 gray-scale levels.

FIG. 6 is a schematic view showing a three-dimensional tomographic imageafter performing volume rendering on the three-dimensional tomographicimage volume data of the fetal head according to general opacitysetting.

FIG. 7 is a setting example of an offset table when it is necessary toenhance the visibility of the ventricle.

FIG. 8 is a schematic view of a three-dimensional tomographic imagegenerated on the basis of the three-dimensional tomographic image volumedata offset-calculated by the offset calculating section on the basis ofthe offset table shown in FIG. 7.

FIG. 9 is a setting example of an offset table when it is necessary toenhance the visibility of the brain substance.

FIG. 10 is a schematic view of a three-dimensional tomographic imagegenerated on the basis of the three-dimensional tomographic image volumedata offset-calculated by the offset calculating section on the basis ofthe offset table shown in FIG. 9.

FIG. 11 is a view showing a display example of a two-dimensionaltomographic image and a brightness-opacity map.

FIG. 12 is a view showing a display example of a three-dimensionaltomographic image, a two-dimensional tomographic image, and abrightness-opacity map.

FIG. 13 is a view showing a display example of a three-dimensionaltomographic image, a two-dimensional tomographic image, and abrightness-opacity map.

FIG. 14 is a view showing the flow of creating a color conversion table.

FIG. 15 is a view showing an example of processing of creating acombined color map table OUTMAP[i] in step 148.

FIG. 16 is a view showing an example of processing of creating acombined color map table OUTMAP[i] in step 148.

FIG. 17 is a block diagram showing the configuration of an ultrasonicdiagnostic apparatus of a second embodiment.

FIG. 18 is a view showing an example of a setting screen of an offsettable used in an offset calculating section.

FIG. 19 is a data flow chart of brightness value conversion processingperformed by the offset calculating section.

FIG. 20 is a block diagram showing the configuration of an ultrasonicdiagnostic apparatus of a third embodiment.

FIG. 21 is a display example when only voxel data (brightness data)which is in a range of the target value of elasticity and the targetbrightness value is visualized by processing of the third embodiment.

FIG. 22 is a display example when only voxel data (brightness data)which is in a range of the target value of elasticity and the targetbrightness value is visualized by processing of the third embodiment.

FIG. 23 is a view showing a display example of a three-dimensionaltomographic image after performing offset calculation processing usingthe threshold value according to the value of elasticity.

FIG. 24 is a view showing a display example of a three-dimensionalelastic image after changing the value of elasticity of a range to bedisplayed using the threshold value according to the value ofelasticity.

FIG. 25 is an example of an image obtained by overlapping RGB componentsafter RGB conversion of the three-dimensional tomographic image and thethree-dimensional elastic image, which are shown in FIGS. 23 and 24,using a blending to add weight.

FIG. 26 is a view showing a display example of an image after performingthe setting of an offset filter according to the brightness using thethreshold value according to the value of elasticity.

FIG. 27 is a view showing a display example of an image after performingthe setting of an offset filter according to the brightness using thethreshold value according to the value of elasticity.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of an ultrasonic diagnostic apparatus, anultrasonic image processing apparatus, an ultrasonic image processingprogram, and an ultrasonic image generation method to which the presentinvention is applied will be described.

(First Embodiment)

A first embodiment of an ultrasonic diagnostic apparatus to which thepresent invention is applied will be described with reference to thedrawings. FIG. 1 is a block diagram showing the entire configuration ofan ultrasonic diagnostic apparatus of a first embodiment.

As shown in FIG. 1, an ultrasonic diagnostic apparatus 100 of thepresent embodiment is configured to include: an ultrasonic probe 2 whichtransmits or receives an ultrasonic wave to or from an object 1; atransmission section 4 which supplies a driving signal to the ultrasonicprobe 2; a receiving section 6 which receives a reflected echo signalreceived by the ultrasonic probe 2; an ultrasonic wave transmission andreception control section 8 which controls transmission and reception ofthe transmission section 4 and the receiving section 6; and a phasingaddition section 10 which generates an RF signal by phase addition ofthe reflected echo signal received by the receiving section 6.

In addition, the ultrasonic diagnostic apparatus 100 includes: atomographic image processing section 12 which generates tomographicimage data by performing various kinds of processing, such aslogarithmic compression, filtering, and image processing, on an RFsignal (ultrasonic signal) output from the phasing addition section 10;a tomographic image volume data generating section 14 which generatesthree-dimensional tomographic image volume data perpendicular to eachaxis by performing coordinate transformation for the tomographic imagedata of plural tomographic planes of the object 1; an offset calculatingsection 16 which is a characteristic section of the present embodimentand which calculates an offset of the brightness value of each voxel ofthe three-dimensional tomographic image volume data; and a tomographicimage volume rendering section 18 which generates a three-dimensionaltomographic image using a volume rendering technique for thethree-dimensional tomographic image volume data offset-calculated.

On the other hand, the ultrasonic diagnostic apparatus 100 includes: atomographic image two-dimensional coordinate transformation section 20which generates a two-dimensional tomographic image on at least onetomographic plane of the three-dimensional tomographic image volume dataon the basis of the output data from the tomographic image processingsection 12; an image combining section 22 which combines thethree-dimensional tomographic image generated by the tomographic imagevolume rendering section 18 and the two-dimensional tomographic imagegenerated by the tomographic image two-dimensional coordinatetransformation section 20; and a display section 24 as a display unitwhich displays an image output from the image combining section 22.

In addition, the ultrasonic diagnostic apparatus 100 includes a controlpanel 26 as an input interface which receives an input, such as acommand from an examiner, and a control section 28 which controls eachof the above components included in the ultrasonic diagnostic apparatus100 on the basis of an input command from the control panel 26. Forexample, when an examiner designates an arbitrary section of thethree-dimensional tomographic image volume data through the controlpanel 26, the information regarding the designated sectional position istransmitted to the tomographic image two-dimensional coordinatetransformation section 20, and a two-dimensional tomographic image atthe sectional position is generated.

Here, each of the above components will be described specifically. Inthe ultrasonic probe 2, transducer elements of 1 to m channels arearrayed in the long-axis direction of the ultrasonic probe. Here, when ktransducer elements are also arrayed in the short-axis direction by 1 tok channels, focusing of transmitted waves or received waves in theshort-axis direction is made by changing a delay time given to each ofthe transducer elements (1 to k channels) in the short-axis direction.In addition, transmitted waves are weighted by changing the amplitude ofan ultrasonic transmission signal given to each transducer element inthe short-axis direction, and received waves are weighted by changingthe amplification or attenuation of an ultrasonic reception signal fromeach transducer element in the short-axis direction. In addition,aperture control can be performed by ON/OFF of each transducer elementin the short-axis direction.

This ultrasonic probe 2 can perform three-dimensional data collection ofthe plural tomographic planes of the object 1 by performing scanningwhile moving in the short-axis direction by motor driving or manuallyaccording to a control signal from the control section 28. In addition,when k transducer elements are also arrayed in the short-axis directionby 1 to k channels, it becomes possible to collect the three-dimensionalultrasonic data by an ultrasonic beam in the short-axis direction alongthe curvature of the probe head or an ultrasonic beam in the short-axisdirection generated by electronic focusing.

In addition, for example, cMUT (Capacitive Micromachined UltrasonicTransducer: IEEE Trans. Ultrason. Ferroelect. Freq. Contr. Vol45 pp. 678to 690 May 1998 and the like) in which the ultrasonic transmission andreception sensitivity, that is, an electromechanical couplingcoefficient changes according to the size of a bias voltage applied in astate superimposed on a driving signal supplied from the transmissionsection 4 can be applied as the ultrasonic probe 2. The cMUT is ahyperfine capacitive ultrasonic transducer manufactured by asemiconductor microfabrication process (for example, LPCVD: Low PressureChemical Vapor Deposition).

The transmission section 4 and the receiving section 6 supply atransmission signal to the ultrasonic probe 2 and also process areceived reflected echo signal. The transmission section 4 and thereceiving section 6 include a transmitter circuit that controls theultrasonic probe 2 to transmit an ultrasonic beam and a receiver circuitthat receives an echo signal of the transmitted ultrasonic beam, whichis reflected from the inside of the object 1, to collect the biologicalinformation and are controlled by the ultrasonic wave transmission andreception control section 8.

The phasing addition section 10 controls the phase of the reflected echosignal output from the receiving section 6 and forms an ultrasonicreceived beam at one point or plural convergent points. In addition, anRF signal generated by the phasing addition section 10 may be complexdemodulated I and Q signals.

The tomographic image processing section 12 processes the reflected echosignal after phase addition in the phasing addition section 10 and isconfigured to include a signal processing circuit, which performslogarithmic compression, filtering, and image processing on the basis ofreflected echo signals input sequentially, and a storage deviceincluding a magnetic disk and a RAM which stores an ultrasonic image.

The tomographic image volume data generating section 14 generates thethree-dimensional tomographic image volume data on the basis of thetomographic image data of the plural tomographic planes processed by thetomographic image processing section 12. The offset calculating section16 calculates an offset of the brightness value for each voxel of thethree-dimensional tomographic image volume data. This will be describedin detail later.

The tomographic image volume rendering section 18 performstwo-dimensional projection processing, such as volume rendering, on thethree-dimensional tomographic image volume data, for which offsetcalculation has been performed, to generate a three-dimensionaltomographic image and transmits it to the image combining section 22.

The tomographic image two-dimensional coordinate transformation section20 generates a two-dimensional tomographic image on at least onetomographic plane of the three-dimensional tomographic image volume dataon the basis of the output data from the tomographic image processingsection 12 by resampling and interpolation processing and transmits thetwo-dimensional tomographic image to the image combining section 22. Theimage combining section 22 combines the three-dimensional tomographicimage generated by the tomographic image volume rendering section 18with the two-dimensional tomographic image generated by the tomographicimage two-dimensional coordinate transformation section 20 and transmitsthe composite image to the display section 24. The display section 24receives the image generated by the image combining section 22 anddisplays the image as an ultrasonic image. The display section 24 isformed by a CRT monitor or an LCD monitor, for example.

Hereinafter, the tomographic image volume rendering section 18 of theultrasonic diagnostic apparatus 100 of the present embodiment will bedescribed more specifically. The tomographic image volume renderingsection 18 generates a projection image (three-dimensional tomographicimage) seen from at least one line-of-sight direction on thetwo-dimensional projection plane on the basis of the three-dimensionaltomographic image volume data, and forms a three-dimensional tomographicimage by multiplying the brightness value in the line-of-sight directionin the three-dimensional tomographic image volume data by thetransparency value for each brightness transmitted by the controlsection 28. Here, expressions of the known volume rendering method usedin the present embodiment are defined below.Cout=Cout-1+(1−Aout-1)·Ai·Ci  (Expression 1)Aout=Aout-1+(1−Aout-1)·Ai  (Expression 2)

In Expression 1, Ci is an i-th voxel brightness value existing on theline of sight when the three-dimensional tomographic image volume datais viewed from a certain point on the two-dimensional projection planegenerated. When data of N voxels is arrayed on the line of sight, thevalue Cout obtained by integration from i=0 to N−1 becomes a last outputpixel value. Cout−1 indicates an integrated value up to the (i−1)-thvalue.

In addition, Ai in Expressions 1 and 2 is the opacity of the i-th voxelvalue on the line of sight, and has a value of 0.0 to 1.0. Both Cout andAout have 0 as initial values. As shown in Expression 2, Aout isintegrated (cumulatively added) each time it passes through the voxeland converges to 1.0. Therefore, as shown in Expression 1, when theintegrated value Aout−1 of the opacity of voxels up to the (i−1)-thvalue becomes about 1.0, the i-th voxel value Ci is reflected on anoutput image. In addition, the transparency when the opacity is set asAi is expressed as 1−Ai, the transparency and the opacity arecomplementary to each other. Accordingly, in this specification, theconcept of transparency and opacity is appropriately described astransparency/opacity. Moreover, for example, even if the opacity isdescribed, the concept of transparency is also described simultaneously.

FIG. 2 is a view showing the relationship between the voxel value andthe opacity. As shown in FIG. 2, the relationship between the voxelvalue and the opacity is generally expressed as an opacity table inwhich the horizontal axis indicates a brightness and the vertical axisindicate an opacity, and the opacity is referred to from the brightnessvalue of a voxel.

From the above, in the volume rendering processing of the presentembodiment, a voxel with high opacity is regarded as a surface so thatthe three-dimensional tomographic image volume data can bestereoscopically displayed. In addition, a maximum value projectionmethod of displaying only a high-brightness structure in a region ofinterest (maximum intensity projection), a minimum value projectionmethod of drawing only a low-brightness structure (minimum intensityprojection), a method of displaying an accumulative image of voxelvalues in the line-of-sight line (Ray summation), or the like isgenerally used as a rendering method of visualizing not the surface butthe inside structure transparently.

Then, a characteristic section of the ultrasonic diagnostic apparatus ofthe present embodiment will be described. The ultrasonic diagnosticapparatus of the present embodiment is an ultrasonic diagnosticapparatus including: the ultrasonic probe 2 which transmits or receivesan ultrasonic wave to or from the object 1; the tomographic image volumedata generating section 14 which generates three-dimensional tomographicimage volume data on the basis of reflected echo signals of pluraltomographic planes of the object 1 measured by the ultrasonic probe 2;the tomographic image volume rendering section 18 which generates athree-dimensional tomographic image seen from at least one line-of-sightdirection on the two-dimensional projection plane on the basis of thethree-dimensional tomographic image volume data; the display section 24which displays a three-dimensional tomographic image; and the offsetcalculating section 16 which increases or decreases the brightness valueof each corresponding voxel according to the brightness value of eachvoxel of the three-dimensional tomographic image volume data. The amountof increase or decrease in the brightness value of each voxel of theoffset calculating section 16 can be adjusted through the inputinterface (control panel) 26, and the tomographic image volume renderingsection 18 generates a three-dimensional tomographic image on the basisof the three-dimensional tomographic image volume data in which thebrightness value is offset by the offset calculating section 16. FIG. 3is a view showing an example of a setting screen of an offset table usedin the offset calculating section 16. FIGS. 3( a) and 3(b) are examplesof setting an offset table.

As shown in FIG. 3, boundary values (P0 to P5) for dividing a range (0to 255) of the brightness value of each voxel of the three-dimensionaltomographic image volume data into plural regions (N: 5 in the presentembodiment) and the amount of increase or decrease (01 to 05) in thebrightness value in each of the plural divided regions are set in theoffset table.

For example, using a graph 31 shown in FIG. 3( a), the boundary ofregions can be set by moving setting pointers of the boundary valuesexpressed as P0 to P5 left and right through the control panel 26.Similarly, 01 to 05 are pointers indicating the amount of increase ordecrease (offset value) in the brightness value of each region, and theoffset value of each region can be set by up-and-down movement. Theupper and lower limits of the graph 31 are set as 100 and −100,respectively. However, this is just an example, and any values may beset if they are in a range of input and output data. In addition, offsetprocessing is not performed for the input brightness value removed fromobjects to be offset due to the movement of P0 or P5. In addition, P0and P5 can also be fixed to both ends of the range of the brightnessvalue of each voxel. In addition, setting of the boundary value (P0 toP5) or the amount of increase or decrease (01 to 05) in the brightnessvalue can be performed using toggle, an encoder, an adjustment button ona liquid crystal panel, or the like.

In addition, regarding the boundary value and the amount of increase ordecrease in the brightness value (offset value), 01 to 05 and P0 to P5in a display window 32 may also be set by a pull-down menu or directnumeric value input through the control panel 26, as shown in FIG. 3(b). In addition, as shown in FIG. 3( b), the number of effective regionsdivided by the boundary values (P0 to P5) may be displayed as the numberof brightness adjustment regions 33 (N=5).

FIG. 4 is a data flow chart of brightness value conversion processingperformed by the offset calculating section 16. As shown in FIG. 4, whenoffset filtering starts in the offset calculating section 16, a counteri is initialized to 0 (step 41). Then, the brightness value m(i) of eachvoxel of the three-dimensional tomographic image volume data is read(step 42). It is determined whether or not i is larger than the totalnumber of data (the number of voxels) (step 43). If i is larger than thetotal number of data (Yes in step 43), the offset filtering ends. On theother hand, if i is not larger than the total number of data, that is,when offset processing is not performed for all voxels of thethree-dimensional tomographic image volume data, the process proceeds tostep 44 in which a counter n for region selection is initialized to 1(step 44).

It is determined whether or not the counter n for region selection issmaller than the number of brightness adjustment regions N (step 45). Ifthe counter n for region selection is smaller than the number ofbrightness adjustment regions N (Yes in step 45), it is determinedwhether or not the i-th read brightness value m(i) of thethree-dimensional tomographic image volume data is in a range of P(n−1)to P(n) (step 46). If Yes in step 46, the amount of increase or decrease(offset value) O(n) in the brightness value is added in step 48 (step48). On the other hand, if No in step 46, the counter n for regionselection is updated and the process returns to step 45 (step 47). Thatis, by the loop of steps 45 to 47, the read i-th brightness value m(i)of the three-dimensional tomographic image volume data is classifiedinto one of the regions divided by the boundary values P(0) to P(N), andthe amount of increase or decrease (offset value) O(n) in the brightnessvalue corresponding to the divided region is added in step 48. After theend of step 48 or if No in step 45, the counter i is updated and theprocess returns to step 42 (step 49).

Through the above processing, the amount of increase or decrease (offsetvalue) O(n) in the brightness value in each of the regions divided bythe boundary values P(0) to P(N) is added to the brightness values ofall voxels of the three-dimensional tomographic image volume data. Inaddition, although the case of performing offset processing using anoffset table is shown in the present embodiment, the present inventionis not limited to this. For example, it is also possible to make theoffset calculating section set a function of outputting the amount ofincrease or decrease in the brightness value according to the input ofthe brightness value of each voxel of the three-dimensional tomographicimage volume data and increase or decrease the brightness value of eachvoxel on the basis of this function.

Next, an example of application of the offset calculating section 16 ofthe present embodiment to the object 1 and the effect will be described.FIG. 5 is a schematic view showing a tomographic image of the fetal headexpressed as brightness values of 256 gray-scale levels. In atomographic image 51, it is assumed that the brightness value ofperiderma 52 is 128. In addition, it is assumed that the brightnessvalue of a fetal skull 53 is 200 and the brightness value of a lumenregion of skull 54 is 32. In addition, it is assumed that the brightnessvalue of brain substance 55 is 80 and the brightness value of aventricle 56 is 16. In addition, it is assumed that the backgroundaround the fetal head is not considered in order to explain the effecteasily.

FIG. 6 shows a three-dimensional tomographic image at the time ofgeneral opacity setting, in which a high-brightness portion is setopaquely and a low-brightness portion is set transparently, whenbuilding a three-dimensional tomographic image for three-dimensionaltomographic image volume data, which is a group of tomographic images,by volume rendering. As shown in FIG. 6, in a three-dimensionaltomographic image 61, a three-dimensional surface image obtained byrendering of the surface of the fetal head, in which most of the outputbrightness is determined by the high-brightness periderma 52 and thefetal skull 53, is formed.

On the other hand, using the offset calculating section 16 of thepresent embodiment, an offset table is set as shown in FIG. 7 when it isnecessary to enhance the visibility of the ventricle 56 as specifictissue that the examiner wants. That is, the offset table includes agraph 71 shown in FIG. 7( a) and a display window 72 shown in FIG. 7(b). In this case, the number of adjustment regions N is 2, and P0 and P2are maximum and minimum values of the input brightness and are fixedvalues. In addition, in order to display only a desired specific targetportion, setting the amount of increase or decrease (offset value) 01 inthe brightness value added to the target portion to 255 and setting theamount of increase or decrease (offset value) 02 of the brightness valueadded to portions other than the target portion to −255 are a method ofdisplaying the target portion most extremely in a three-dimensionalmanner. Since the boundary value P1 is set while checking an image, theboundary value P1 can be set through the control panel 26 by theexaminer.

FIG. 8 is a schematic view of a three-dimensional tomographic imagegenerated on the basis of three-dimensional tomographic image volumedata offset-calculated by the offset calculating section 16 on the basisof the offset table shown in FIG. 7. Since the brightness value of theventricle 56 is 16 which is in a range of P0(0) to P1(17), an offset of+255 is made. Since other tissue is in a range of P1(17) to P2(255), anoffset of −255 is made. Accordingly, as shown in FIG. 8, athree-dimensional tomographic image 81 is generated and displayed as athree-dimensional tomographic image in which the visibility of theventricle 56 is enhanced. Moreover, when highlight display from thesmallest brightness value to the arbitrary brightness value is necessaryas in this example, the three-dimensional tomographic image shown inFIG. 8 can be generated with a simple operation by arbitrarily setting aparameter “display threshold value” and the amount of increase ordecrease (offset value) in the brightness value using toggle, anencoder, an adjustment button on a liquid crystal panel, or the like.

On the other hand, when it is necessary to enhance the visibility of thebrain substance 55 as specific tissue that the examiner wants, an offsettable is set as shown in FIG. 9. That is, as shown in FIG. 5, theventricle 56 with low brightness is present inside the brain substance55, the lumen region of skull 54 with low brightness similar to theabove is present around the brain substance 55, and the fetal skull 53is present around the lumen region of skull 54. Accordingly, thebrightness range with the enhanced visibility is one region withintermediate brightness. Therefore, in the offset table, as in a graph91 shown in FIG. 9( a) and a display window 92 shown in FIG. 9( b), itis assumed that the number of adjustment regions N is 3, P0 and P3 arefixed to minimum and maximum values of the input brightness, and theamount of increase or decrease (offset value) in the brightness value isset to 01=−255, 02=255, and 03=−255. The boundary values P1 and P2 canbe arbitrarily set through the control panel 26 while checking theimage.

FIG. 10 is a schematic view of a three-dimensional tomographic imagegenerated on the basis of three-dimensional tomographic image volumedata offset-calculated by the offset calculating section 16 on the basisof the offset table shown in FIG. 9. Since the brightness value of thebrain substance 55 is 80 which is in a range of P1(75) to P2(85), anoffset of +255 is made. Since other tissue is in a range of P0(0) toP1(75) or a range of P2(85) to P3(255), an offset of −255 is made.Accordingly, as shown in FIG. 10, a three-dimensional tomographic image101 is generated and displayed as a three-dimensional tomographic imagein which the visibility of the brain substance 55 is enhanced. Moreover,when it is necessary to highlight an arbitrary brightness rangecorresponding to the intermediate brightness as in this example, thethree-dimensional tomographic image shown in FIG. 10 can be generatedwith a simple operation by arbitrarily setting parameters “display startthreshold value” and “display end threshold value” and the amount ofincrease or decrease (offset value) in the brightness value usingtoggle, an encoder, an adjustment button on a liquid crystal panel, orthe like.

In addition, since setting using toggle or an encoder is difficult whenthere are two or more desired specific tissue portions (targetportions), it is preferable to edit a setting screen on the displayscreen directly. An increase or decrease in the number of brightnessadjustment regions N on the liquid crystal panel on the display from thecontrol panel 26, the boundary values P0 to Pn, and offsets O0 to On canbe set by a track ball operation in the control panel 26 or a touchpanel on the display section 24. In addition, they may also be set bythe control panel 26 using a pull-down menu (up-and-down bar) in thedisplay window 32.

In addition, although the example in which an examiner adjusts theoffset table through the control panel 26 is shown in the presentembodiment, the present invention is not limited to this. For example,plural offset tables, such as an offset table for enhancing thevisibility of tissue with low brightness value, an offset table forenhancing the visibility of tissue with intermediate brightness value,and an offset table for enhancing the visibility of tissue with highbrightness value, may be prepared as default and an examiner may selectan offset table to be used. According to this, the examiner can obtain athree-dimensional tomographic image, in which the visibility of desiredspecific tissue is enhanced, with a simple operation.

Then, a two-dimensional tomographic image as an auxiliary screen whensetting an offset table will be described using FIGS. 11 to 13. FIG. 11is a view showing a display example of a two-dimensional tomographicimage and a brightness-opacity map. FIG. 11( a) shows a two-dimensionaltomographic image, and FIG. 11( b) shows a brightness-opacity map. Asshown in FIG. 11( b), in a brightness-opacity map 111, a color codeusing a two-dimensional table in which the vertical axis indicatesbrightness and the horizontal axis indicates opacity is set. That is,the color code is set according to the brightness value and thetransparency/opacity. Moreover, in a two-dimensional tomographic image112, a color is given according to the color code of thebrightness-opacity map 111, as shown in FIG. 11( a). A dotted line inthe brightness-opacity map 111 is equivalent to the line showing therelationship between the voxel value and the opacity shown in FIG. 2,the opacity with respect to the input brightness value is determineduniquely, and the color of a pixel displayed on the two-dimensionaltomographic image 112 is determined at one point on the dotted line ofthe brightness-opacity map 111.

The tomographic image data as the basis of the two-dimensionaltomographic image 112 is generated by the tomographic imagetwo-dimensional coordinate transformation section 20. The tomographicimage data is tomographic image data of the arbitrary section of thethree-dimensional tomographic image volume data designated through thecontrol panel 26 by the examiner, and offset processing by the offsetcalculating section 16 is not performed on the tomographic image data.The tomographic image data is input to the image combining section 22.The image combining section 22 acquires from the control section 28 theboundary value of the offset table, the amount of increase or decrease(offset value) in the brightness, and the brightness-opacity map 111.

The image combining section 22 offsets the brightness value of thetomographic image data input from the tomographic image two-dimensionalcoordinate transformation section 20 on the basis of the offset tableand converts a color of each voxel of the offset tomographic image dataon the basis of the brightness-opacity map 111 to generate atwo-dimensional tomographic image. For example, conversion into numericvalue with color information, such as RGB or YUV is performed referringto the brightness value and the opacity of each voxel of the tomographicimage data in which the brightness value has been offset. In such colorcode conversion processing, by setting the brightness value on thevertical axis like the brightness-opacity map 111 and setting color datawith a high chroma, which is not relevant to the input data, as theopacity decreases on the horizontal axis, it is possible to display atransmissive region, a non-transmissive region, and an intermediateregion in a three-dimensional tomographic image in a stepwise manner.

For example, in FIG. 11, in the two-dimensional tomographic image 112,an opaque region 113 dominant in a three-dimensional tomographic image,an intermediate region 114 with low transparency having a large effecton a three-dimensional tomographic image, an intermediate region 115with high transparency having little effect on a three-dimensionaltomographic image, and a transparent region 116 having no effect on athree-dimensional tomographic image are displayed after being encodedwith different hues from the brightness. As a result, since the examinercan grasp intuitively the influence of the boundary value and the amountof increase or decrease (offset value) in the brightness value on thethree-dimensional tomographic image, the examination efficiency can beimproved. That is, the examiner can recognize which region on thetwo-dimensional tomographic image 112 is reflected on thethree-dimensional tomographic image and which region is not reflected.For example, since a region of the transparent region 116 is notreflected on the three-dimensional tomographic image in current settingof the offset table, it can be seen that the setting of the offset tableshould be adjusted if it is reflected.

FIG. 12 is a view showing a display example of a three-dimensionaltomographic image, a two-dimensional tomographic image, and abrightness-opacity map. As shown in FIG. 12, a three-dimensionaltomographic image 121, a two-dimensional tomographic image 122, and abrightness-opacity map 123 are displayed side by side. Referring to FIG.12, the examiner can recognize that the opaque region 113 is drawnopaquely, the transparent region 116 is not drawn at all, and theintermediate regions 114 and 115 are drawn translucently. In addition, atarget portion can be clearly visualized by emphasizing the opaqueregion 113.

FIG. 13 is a view showing a display example of a three-dimensionaltomographic image, a two-dimensional tomographic image, and abrightness-opacity map. As shown in FIG. 13, a three-dimensionaltomographic image 131, a two-dimensional tomographic image 132 on theX-Y tomographic plane, a two-dimensional tomographic image 133 on theX-Z tomographic plane, a two-dimensional tomographic image 134 on theY-Z tomographic plane, and a brightness-opacity map 135 are displayedside by side. By displaying the sections simultaneously from threedirections as described above, it is possible to enable the examiner tounderstand the visualization region more clearly.

Then, an example of a method of creating a color conversion table(brightness-opacity map) used in the above color code conversionprocessing will be described using FIGS. 14 to 16. FIG. 14 is a viewshowing the flow of creating a color conversion table. It is assumedthat symbols P and O described in FIG. 14 indicate the above-describedboundary value P(n) and the amount of increase or decrease (offsetvalue) O(n) in the brightness value, respectively.

Moreover, in FIGS. 15 and 16, a color conversion table OUTMAP[i] used inthe present embodiment indicates a combined color map table, BWMAP[i]indicates an RGB conversion table for tomographic image output, andCOLMAP[i] indicates an RGB color table for transparency setting. Theseare tables for performing conversion into natural colors by returningthree elements of R, G, and B, which are three primary colors, to theinput i, and each table is a color map table accessible to threeelements of RGB by *.R, *.G, and *.B. i indicates a gray-scale levelaccording to the input brightness. 256 gray-scale levels of 0 to 255 areused in many cases, but any number may be used.

In the RGB table for transparency setting COLMAP, for example, *.R=0,*.G=255, and *.B=0 may be set for all gradation elements i and becominggreen according to an increase in transparency may be set, or anarbitrary visual effect may be given by setting different hues, chroma,and brightness for the gradation element i.

As shown in FIG. 14, when color map conversion processing starts, theinput gradation value (indicating the input brightness value, the valueof elasticity, or other inputs) expressed by the counter i isinitialized to 0 (step 141). Then, size comparison between the counter iand Mmap (the number of gray-scale levels of a map) is performed (step142). If i is smaller than Mmap (No in step 142), the process proceedsto step 143. The counter for region selection n is initialized to 1 instep 143, the selected input gradation value i is classified into one ofthe regions divided by the boundary values P(0) to P(N) in steps 144 and145, opacity mm(i) is calculated with reference to an opacity tableOPQ[n] using a value obtained by adding the amount of increase ordecrease (offset value) O(n) in the brightness value selected in step146 to i, and a combined color map table OUTMAP[i] is created using theopacity mm(i) in step 148.

A constant v used in step 146 is a parameter for having an effect of anopaque color, and is normally set to 1.0. Steps 143 and 147 areinitialization processing and update processing of the counter n forregion selection, respectively, and step 149 is update processing of thecounter i.

FIG. 15 is a view showing an example of the processing of creating thecombined color map table OUTMAP[i] in step 148. As shown in FIG. 15, instep 151, each element of OUTMAP[i] is calculated as a value obtained byadding a value, which is obtained by multiplication of BWMAP[i] andmm(i), and a value, which is obtained by multiplication of COLMAP [i]and (1.0-mm(i)).

This indicates that the color map table OUTMAP[i] is created in whichwhen *.R=0, *.G=255, and *.B=0 are set for all gradation elements i inthe RGB table COLMAP for transparency setting, the tomographic imagebrightness BWMAP[i] is output as it is in the case of the opaque inputgradation value i and a tomographic image becoming gradually greenaccording to a decrease in opacity is output in the case of thetransparent input gradation value i, for example.

That is, a region of a tomographic image formed as an opaquethree-dimensional voxel is displayed in black and white or a tomographicimage with a set color tone is displayed, a region of a tomographicimage formed as a transparent three-dimensional voxel is displayed witha color for transparency setting other than the set color tone, and thecolor for transparency setting is displayed with a high ratio on thetomographic image according to change from opacity to transparency.

At this time, although a completely green color appears in the case ofthe completely opaque input gradation value i, the constant v used instep 146 is set to 1.0 or less (for example, 0.9 or 0.8) so that it ispossible to adjust the condition of coloring, such as translucence.Accordingly, since the region of the completely opaque input gradationvalue i becomes translucent green instead of complete green, theexaminer can recognize the shape of the region and the like visually.

FIG. 16 is a view showing an example of the processing of creating thecombined color map table OUTMAP[i] in step 148. In step 161, the RGBcolor table for transparency setting is not prepared, and the combinedcolor map table OUTMAP is created in a simple way by calculating acomposite color with the fixed color value for transparency settingusing the opacity coefficient mm(i).

The above-described two examples are examples of a method of combiningeach element of the RGB color map with the opacity coefficient mm(i).However, it is also possible to store the color information in the HSVformat, in which the chroma, brightness, and hue are stored asparameters, and to perform combining processing using those obtained bychanging these parameters by mm(i). The output format is not limited tothe RGB format, and a YIN method may also be used.

(Second Embodiment)

A second embodiment of an ultrasonic diagnostic apparatus to which thepresent invention is applied will be described with reference to thedrawings. FIG. 17 is a block diagram showing the configuration of theultrasonic diagnostic apparatus of the second embodiment. The sameconfiguration as in the first embodiment will not be described.

As shown in FIG. 17, the ultrasonic diagnostic apparatus 100 includes:an RF signal frame data selecting section 171 which stores RF signalframe data output from the phasing addition section 10 and which selectsat least two items of the frame data; a displacement measuring section172 which measures the displacement of body tissue of an object; anelastic information calculating section 173 which calculates thedistortion or the elastic modulus from the displacement informationmeasured by the displacement measuring section 172; an elastic imageprocessing section 174 which forms a color elastic image from thedistortion or the elastic modulus calculated by the elastic informationcalculating section 173; and an elastic image two-dimensional coordinatetransformation section 177 which converts an output signal from theelastic image processing section 174 so as to fit the display of thedisplay section 24.

In addition, the ultrasonic diagnostic apparatus 100 includes an elasticimage volume data generating section 175 which generates elastic imagevolume data by performing coordinate transformation to three-dimensionalelastic data on the basis of an output signal from the elastic imageprocessing section 174 and an elastic image volume rendering section 176which performs volume rendering, maximum and minimum values projection,or averaging processing on the elastic image volume data, which ispresent in the line-of-sight direction of each pixel on thetwo-dimensional projection plane, on the basis of an output signal fromthe elastic image volume data generating section 175.

The RF signal frame data selecting section 171 stores plural RF signalframe data items from the phasing addition section 10 and selects a pairof RF signal frame data items, that is, two items of the RF signal framedata from the stored RF signal frame data group. For example, RF signalframe data from the phasing addition section 10 generated in timeseries, that is, on the basis of the frame rate of an image issequentially stored in the RF signal frame data selecting section 171,and the stored RF signal frame data (N) is selected as first data and atthe same time, one RF signal frame data item (X) is selected from the RFsignal frame data group (N−1, N−2, N−3, . . . , N−M) previously stored.In addition, N, M, and X herein are index numbers given to the RF signalframe data, and are assumed to be natural numbers.

In addition, the displacement measuring section 172 performsone-dimensional or two-dimensional correlation processing on a pair ofselected data, that is, the RF signal frame data (N) and the RF signalframe data (X) to calculate a displacement or movement vector in bodytissue corresponding to each point of the tomographic image, that is,one-dimensional or two-dimensional displacement distribution regardingthe displacement direction and size. Here, a block matching method isused to detect a movement vector. The block matching method is toperform processing in which an image is divided into blocks with, forexample, “N×N” pixels, a block in a region of interest is observed, themost similar block to the observed block is searched for from previousframes, and a sample value is determined by predictive coding, that is,by the difference referring to this.

The elastic information calculating section 173 calculates thedistortion or the elastic modulus of body tissue corresponding to eachpoint on the tomographic image from the measurement value output fromthe displacement measuring section 172, for example, the movement vectorand the pressure value, which is output from a pressure measuringsection 178, and generates an elastic image signal, that is, elasticframe data, on the basis of the distortion or the elastic modulus.

In this case, the data of the distortion is calculated by spatialdifferentiation of the amount of movement of body tissue, for example,by spatial differentiation of the displacement. In addition, in theconfiguration with a pressure measuring function as shown in thepressure measuring section 178, the elastic modulus can be calculatedand the elastic modulus may also be used as elastic data accordingly.The data of the elastic modulus is calculated by dividing the pressurechange by a distortion change. For example, assuming that thedisplacement measured by the displacement measuring section 172 is L(X)and the pressure measured by the pressure measuring section 178 is P(X),distortion ΔS(X) can be calculated by spatial differentiation of L(X).Accordingly, the distortion ΔS(X) can be calculated using ExpressionΔS(X)=ΔL(X)/ΔX. In addition, the Young's modulus Ym(X) of elasticmodulus data is calculated by Expression of Ym=(ΔP(X))/ΔS (X). Since theelastic modulus of body tissue corresponding to each point of thetomographic image is calculated from this Young's modulus Ym, it ispossible to acquire the two-dimensional elastic image data continuously.In addition, the Young's modulus is a ratio of simple tensile stressapplied to the object to the tensile strain occurring in parallel to thetensile stress.

The elastic image processing section 174 is configured to include aframe memory and an image processing section. The elastic imageprocessing section 174 secures the elastic frame data, which is outputin time series from the elastic information calculating section 173, inthe frame memory and performs image processing on the secured elasticframe data. In addition, the elastic image processing section 174evaluates an error of an elastic image from the output information ofthe RF signal frame data selecting section 171, the displacementmeasuring section 172, or the elastic information calculating section173 and performs masking of the output image.

The elastic image two-dimensional coordinate transformation section 177performs coordinate transformation of the elastic frame data from theelastic image processing section 174 so as to fit the monitor. Inaddition, the ultrasonic probe 2 can perform scanning in the short-axisdirection manually or by motor driving according to a control signalfrom the control section 28. In addition, in the case of a configurationincluding a magnetic sensor 179 even if manual scanning is performed, itis possible to detect the amount of compression or the short axisposition by using the positional information from the magnetic sensor179.

The elastic image volume data generating section 175 performs coordinatetransformation to the three-dimensional elastic data from the elasticimage processing section 174, and the elastic image volume renderingsection 176 performs volume rendering, maximum and minimum valuesprojection, or average processing on the output volume data present inthe line-of-sight direction of each pixel on the two-dimensionalprojection plane.

The image combining section 22 combines a tomographic image with thetomographic data and the distortion/elastic data generated by theelastic image volume rendering section. The brightness information andthe hue information regarding each pixel of the composite image are forgenerating an image displayed on the display section 24 by addinginformation on a monochrome tomographic image and information on a colorelastic image with a mixing ratio and performing RGB conversion.

Here, the offset calculating section 16 converts the brightness of thethree-dimensional tomographic image volume data output from thetomographic image volume data generating section 14 using thethree-dimensional elastic image data and transmits the three-dimensionaltomographic image volume data to the tomographic image volume renderingsection 18. In other words, the offset calculating section 16 of thepresent embodiment increases or decreases the brightness value of eachcorresponding voxel of the three-dimensional tomographic image volumedata, which is output from the tomographic image volume data generatingsection 14, according to the value of elasticity of each voxel of thethree-dimensional elastic image volume data output from the elasticimage volume data generating section 175.

In addition, the elastic image data is a generic term for elasticparameters indicating the stiffness, such as the strain, Young'smodulus, longitudinal modulus, and transverse modulus calculated by themethod described above, and is assumed not to indicate a specific one.

Then, a characteristic section of the ultrasonic diagnostic apparatus ofthe present embodiment will be described. FIG. 18 is a view showing anexample of a setting screen of an offset table used in the offsetcalculating section 16. FIGS. 18( a) and 18(b) are examples of settingan offset table.

As shown in FIG. 18, boundary values (E0 to E5) for dividing a range (0to 255) of the value of elasticity of each voxel of thethree-dimensional elastic image volume data into plural regions (N: 5 inthe present embodiment) and the amount of increase or decrease (01 to05) in the brightness value in each of the plural divided regions areset in the offset table.

For example, using a graph 181 shown in FIG. 18( a), the boundary ofregions can be set by moving setting pointers of the boundary valuesexpressed as E0 to E5 left and right through the control panel 26.Similarly, 01 to 05 are pointers indicating the amount of increase ordecrease (offset value) in the brightness value of each region, and theoffset value of each region can be set by up-and-down movement. Theupper and lower limits of the graph 181 are set as 100 and −100,respectively. However, this is just an example, and any values may beset if they are in a range of input and output data. In addition, offsetprocessing is not performed for the input value of elasticity removedfrom objects to be offset due to the movement of E0 or E5. In addition,E0 and E5 can also be fixed to both ends of the range of the value ofelasticity of each voxel. In addition, setting of the boundary value (E0to E5) or the amount of increase or decrease (01 to 05) in thebrightness value can be performed using toggle, an encoder, anadjustment button on a liquid crystal panel, or the like.

In addition, regarding the boundary value and the amount of increase ordecrease in the brightness value (offset value), 01 to 05 and E0 to E5in a display window 182 may also be set by a pull-down menu or directnumeric value input through the control panel 26, as shown in FIG. 18(b). In addition, as shown in FIG. 18( b), the number of effectiveregions divided by the boundary values (E0 to E5) may be displayed asthe number of brightness adjustment regions 183 (N=5).

FIG. 19 is a data flow chart of brightness value conversion processingperformed by the offset calculating section 16. As shown in FIG. 19,when offset filtering starts in the offset calculating section 16, acounter i is initialized to 0 (step 191). Then, the brightness valuem(i) of each voxel of the three-dimensional tomographic image volumedata and the value of elasticity e(i) of each voxel of thethree-dimensional elastic image volume data are read (step 192). It isdetermined whether or not i is larger than the total number of data (thenumber of voxels) (step 193). If i is larger than the total number ofdata (Yes in step 193), the offset filtering ends. On the other hand, ifi is not larger than the total number of data, that is, when offsetprocessing is not performed for all voxels of the three-dimensionaltomographic image volume data, the process proceeds to step 194 in whicha counter n for region selection is initialized to 1 (step 194).

It is determined whether or not the counter n for region selection issmaller than the number of brightness adjustment regions N (step 195).If the counter n for region selection is smaller than the number ofbrightness adjustment regions N (Yes in step 195), it is determinedwhether or not the i-th read value of elasticity e(i) of thethree-dimensional elastic image volume data is in a range of E(n−1) toE(n) (step 196). If Yes in step 196, the amount of increase or decrease(offset value) O(n) in the brightness value is added to the brightnessvalue of a corresponding voxel of the three-dimensional tomographicimage volume data in step 198 (step 198). On the other hand, if No instep 196, the counter n for region selection is updated and the processreturns to step 195 (step 197).

That is, by the loop of steps 195 to 197, the read i-th value ofelasticity e(i) of the three-dimensional elastic image volume data isclassified into one of the regions divided by the boundary values E(0)to E(N). Then, in step 198, the amount of increase or decrease (offsetvalue) O(n) in the brightness value corresponding to the divided regionis added to the brightness value of a corresponding voxel of thethree-dimensional tomographic image volume data. After the end of step198 or if No in step 195, the counter i is updated and the processreturns to step 192 (step 199).

Through the above processing, the amount of increase or decrease (offsetvalue) O(n) in the brightness value in each of the regions divided bythe boundary values E(0) to E(N) is added to the brightness values ofall voxels of the three-dimensional tomographic image volume data. Inaddition, although the case of performing offset processing using anoffset table is shown in the present embodiment, the present inventionis not limited to this. For example, it is also possible to set, in theoffset calculating section, a function of outputting the amount ofincrease or decrease in the brightness value of a corresponding voxel ofthe three-dimensional tomographic image volume data according to theinput of the value of elasticity of each voxel of the three-dimensionalelastic image volume data and to increase or decrease the brightnessvalue of the corresponding voxel of the three-dimensional tomographicimage volume data on the basis of this function.

Similar to the first embodiment, the image combining section 22 displaysthe two-dimensional tomographic image with the three-dimensionaltomographic image on the basis of the output from the tomographic imagetwo-dimensional coordinate transformation section 20 and the output fromthe tomographic image volume rendering section 18. In addition to this,in the present embodiment, a three-dimensional elastic image obtained byprojecting the three-dimensional elastic image volume data onto thetwo-dimensional projection plane may also be displayed on the imagecombining section 22 on the basis of the output from the elastic imagevolume rendering section 176.

According to the present embodiment, an examiner can generate athree-dimensional tomographic image with enhanced visibility of tissue,which has a specific value of elasticity, on the basis of the value ofelasticity (stiffness or softness of tissue) of desired specific tissue.For example, if the examiner knows the value of elasticity of desiredspecific tissue, it is possible to enlarge the amount of increase(offset amount) in the brightness value corresponding to the vicinity ofthe value of elasticity in advance. On the other hand, when the examinerwants to observe hard (or soft) tissue, a three-dimensional tomographicimage of the hard (or soft) tissue with high visibility is displayed ifthe amount of increase (offset amount) in the brightness valuecorresponding to the high (or low) value of elasticity is set high. As aresult, it becomes easy to observe the hard (or soft) tissue.

(Third Embodiment)

A third embodiment of an ultrasonic diagnostic apparatus to which thepresent invention is applied will be described with reference to thedrawings. FIG. 20 is a block diagram showing the configuration of theultrasonic diagnostic apparatus of the third embodiment. As shown inFIG. 20, the present embodiment is different from the ultrasonicdiagnostic apparatus of the second embodiment in that the output of theelastic image volume data generating section 175 is input to thetomographic image volume rendering section 18 and the tomographic imagevolume rendering section 18 can refer to the three-dimensional elasticimage volume data. Explanation regarding the other same parts as in thesecond embodiment will be omitted. In the present embodiment, a functionof generating a three-dimensional tomographic image that an examinerwants using both the three-dimensional tomographic image volume data andthe three-dimensional elastic image volume data is given.

In the present embodiment, the offset calculating section 16 isconfigured to increase or decrease the brightness value of each voxelaccording to the brightness value of each voxel of the three-dimensionaltomographic image volume data in the same manner as in the firstembodiment.

In addition, the control panel 26 has a function of setting thethreshold value according to the value of elasticity, and theinformation regarding the threshold value of the value of elasticity setby the control panel 26 is set in the tomographic image volume renderingsection 18 through the control section 28. In the present embodiment,when performing volume rendering of a tomographic image using theabove-described Expressions (1) and (2), the tomographic image volumerendering section 18 sets the opacity Ai in Expression (1) to 0 for acorresponding voxel if the value of elasticity of each voxel exceeds (oris less than) the threshold value of the value of elasticity.

Then, brightness conversion of the input brightness value is performedby offset calculation processing. Even if it is opaque, that is, becomesa brightness value to be displayed as a result of comparison using anopacity table, it becomes transparent when the value of elasticity isnot present in a target region. As a result, it becomes possible tovisualize only the voxel data (brightness data) which is in a range ofthe target value of elasticity and the target brightness value.

FIG. 21 is a display example when only the voxel data (brightness data)which is in a range of the target value of elasticity and the targetbrightness value is visualized by processing of the present embodiment.As shown in FIG. 21, it is possible to display a three-dimensionaltomographic image 211, in which only the voxel data (brightness data)that is in a range of the target value of elasticity and the targetbrightness value is visualized, and images 212 and 213, in which atomographic image and an elastic image on the arbitrary section of thethree-dimensional tomographic image 211 overlap each other, side byside.

These images 212 to 214 are generated by the tomographic imagetwo-dimensional coordinate transformation section 20 and the elasticimage two-dimensional coordinate transformation section 177 and areoverlapped using a method, such as a blending, after color codingprocessing in the image combining section 22. In addition, as theseimages 212 and 213, not only three images shown in the drawing but alsoan arbitrary number of slice images may be simultaneously displayed.

Using the threshold value of the value of elasticity set by the controlpanel 26, the elastic image volume rendering section 176 can visualizeonly the surface of an image in the effective display range by settingthe value of elasticity of a range, which is to be displayed, to 1.0 andthe opacity of a range, which is not to be displayed, to 0.0. Inaddition, referring to the input brightness of the tomographic imagevolume data generating section 14, it is possible to visualize only thesurface of an image in the effective display range by setting the valueof elasticity of a region, in which the opacity of the input brightnessis not 0, to 1.0 and the opacity of a range, in which the opacity of theinput brightness is 0, to 0.0.

FIG. 22 is a display example when only the voxel data (brightness data)that is in a range of the target value of elasticity and the targetbrightness value is visualized by processing of the present embodiment.As shown in FIG. 22, it is possible to display a three-dimensionaltomographic elastic image 221 and images 222 to 224, in which atomographic image and an elastic image on the arbitrary section of thethree-dimensional tomographic elastic image 221 overlap each other, sideby side. The three-dimensional tomographic elastic image 221 is formedby overlapping an image, which is obtained by setting the value ofelasticity of the image surface in a three-dimensional manner using themethod described above, and an image, which is obtained by setting in athree-dimensional manner the voxel data (brightness data) that is atarget value of elasticity and is in a range of a target brightnessvalue, with each other using a method, such as a blending, in the imagecombining section 22. Compared with the three-dimensional tomographicimage 211, it is possible to intuitively distinguish the informationregarding the hardness since color display is performed according to theelastic image.

FIG. 23 is a view showing a display example of a three-dimensionaltomographic image using the threshold value according to the value ofelasticity described in the above paragraph. At this time, the case inwhich offset calculation processing is given but setting of an offsetfilter according to the brightness is not performed is shown in theexample. FIGS. 23( a), 23(b), and 23(c) show a three-dimensionaltomographic image 231 when there is no threshold value (all displayed),a three-dimensional tomographic image 232 when the threshold value isset to an intermediate value (part of the soft tissue is not displayed),and a three-dimensional tomographic image 233 when the threshold valueis set to a high value (only the hard tissue is displayed),respectively.

For example, in the three-dimensional tomographic image 231, it isdifficult to observe a depth-direction shape of cylindrical hard tissue,which is formed in a phantom and has low inside brightness. On the otherhand, it is possible to gradually make a cylindrical low-brightnessregion, which is formed in the phantom, easily observable by changingthe setting of the threshold value of the value of elasticity as in thethree-dimensional tomographic images 232 and 233.

FIG. 24 is a view showing a display example of a three-dimensionalelastic image after the value of elasticity of a range to be displayedis changed using the threshold value according to the value ofelasticity. FIGS. 24( a), 24(b), and 24(c) show a three-dimensionalelastic image 241 when there is no threshold value (all displayed), athree-dimensional elastic image 242 when the threshold value is set toan intermediate value (part of the soft tissue is not displayed), and athree-dimensional elastic image 243 when the threshold value is set to ahigh value (only the hard tissue is displayed), respectively.

Similarly, also in this example, it is difficult to observe acylindrical low-brightness region formed in a phantom in thethree-dimensional elastic image 241. However, it is possible togradually make the cylindrical low-brightness region, which is formed inthe phantom, easily observable by changing the setting of the thresholdvalue of the value of elasticity as in the three-dimensional elasticimages 242 and 243.

FIG. 25 is an example of an image obtained by overlapping RGB componentsafter RGB conversion of the three-dimensional tomographic image and thethree-dimensional elastic image, which are shown in FIGS. 23 and 24,using a blending to add weight. That is, FIGS. 25( a), 25(b), and 25(c)show a three-dimensional tomographic elastic image 251 when there is nothreshold value (all displayed), a three-dimensional tomographic elasticimage 252 when the threshold value is set to an intermediate value (partof the soft tissue is not displayed), and a three-dimensionaltomographic elastic image 253 when the threshold value is set to a highvalue (only the hard tissue is displayed), respectively.

Similarly, also in this example, it is difficult to observe acylindrical low-brightness region formed in a phantom in thethree-dimensional tomographic elastic image 251. However, it is possibleto gradually make the cylindrical low-brightness region, which is formedin the phantom, easily observable by changing the setting of thethreshold value of the value of elasticity as in the three-dimensionaltomographic elastic images 252 and 253. In addition, by displaying thethree-dimensional tomographic image and the three-dimensional elasticimage so as to overlap each other, an image further suitable fordiagnosis can be provided to the examiner.

Next, FIGS. 26 and 27 show image display examples after performing thesetting of an offset filter according to the brightness using thethreshold value processing according to the value of elasticitydescribed in the above paragraph. The offset is set so as to emphasize atarget observation portion with low brightness and to suppress a portionwith brightness equal to or higher than that of the target observationportion.

FIG. 26 shows a display example of a three-dimensional tomographic imageafter performing the setting of an offset filter according to thebrightness using the threshold value according to the value ofelasticity described in the above paragraph. FIGS. 26( a), 26(b), and26(c) show a three-dimensional tomographic image 261 when there is nothreshold value (all displayed), a three-dimensional tomographic image262 when the threshold value is set to an intermediate value (part ofthe soft tissue is not displayed), and a three-dimensional tomographicimage 263 when the threshold value is set to a high value (only the hardtissue is displayed), respectively.

For example, in the three-dimensional tomographic image 261, it isdifficult to observe a depth-direction shape of cylindrical hard tissue,which is formed in a phantom and has low inside brightness. On the otherhand, it is possible to gradually make a cylindrical low-brightnessregion, which is formed in the phantom, easily observable by changingthe setting of the threshold value of the value of elasticity as in thethree-dimensional tomographic images 262 and 263.

FIG. 27 is an example of an image obtained by overlapping RGB componentsafter RGB conversion of the three-dimensional tomographic image and thethree-dimensional elastic image after performing the setting of anoffset filter according to the brightness using the threshold valueaccording to the value of elasticity, which are shown in FIG. 26, usinga blending to add weight. That is, FIGS. 27( a), 27(b), and 27(c) show athree-dimensional elastic image 271 when there is no threshold value(all displayed), a three-dimensional elastic image 272 when thethreshold value is set to an intermediate value (part of the soft tissueis not displayed), and a three-dimensional elastic image 273 when thethreshold value is set to a high value (only the hard tissue isdisplayed), respectively.

Similarly, also in this example, it is difficult to observe acylindrical low-brightness region formed in a phantom in thethree-dimensional tomographic elastic image 271. However, it is possibleto gradually make the cylindrical low-brightness region, which is formedin the phantom, easily observable by changing the setting of thethreshold value of the value of elasticity as in the three-dimensionaltomographic elastic images 272 and 273. In addition, by displaying thethree-dimensional tomographic image and the three-dimensional elasticimage so as to overlap each other, an image further suitable fordiagnosis can be provided to the examiner.

In addition, when performing the setting of an offset filter accordingto the brightness using the threshold value according to the value ofelasticity as shown in FIGS. 26 and 27, a low-brightness targetobservation portion is emphasized by offset processing and displayedwith high brightness and a part of a high-brightness peripheral portionis suppressed. On the other hand, the threshold value processing is setso as to display hard tissue and remove soft tissue. Accordingly, a hardtarget observation portion is displayed and a part of a soft peripheralportion is removed. As a result, since an unnecessary portion whichcannot be removed in either the offset processing or the threshold valueprocessing is removed from the three-dimensional image, a targetobservation portion can be further emphasized and displayed comparedwith FIGS. 23 and 25.

In addition, although the ultrasonic diagnostic apparatus and theultrasonic image generation method have been mainly described in theabove embodiments, the present invention is not limited to these. Forexample, the present invention may be applied to an ultrasonic imageprocessing apparatus such as a PC which generates a three-dimensionaltomographic image off-line for three-dimensional tomographic imagevolume data of an object generated in advance by an ultrasonicdiagnostic apparatus. In addition, the present invention may also beapplied to an ultrasonic image processing program installed in a medicalimage processing apparatus, such as a PC.

That is, the ultrasonic image processing apparatus, such as a PC, towhich the present invention is applied may be configured to include: amemory in which three-dimensional tomographic image volume datagenerated on the basis of reflected echo signals of plural tomographicplanes of an object measured by an ultrasonic probe is stored; atomographic image volume rendering section which generates athree-dimensional tomographic image seen from at least one line-of-sightdirection on the two-dimensional projection plane on the basis of thethree-dimensional tomographic image volume data stored in the memory;and a display section which displays the three-dimensional tomographicimage.

In addition, the ultrasonic image processing apparatus includes anoffset calculating section which increases or decreases the brightnessvalue of each voxel according to the brightness value of each voxel ofthe three-dimensional tomographic image volume data. The amount ofincrease or decrease in the brightness value of each voxel of the offsetcalculating section can be adjusted through an input interface. Thetomographic image volume rendering section may be configured to generatea three-dimensional tomographic image on the basis of thethree-dimensional tomographic image volume data in which the brightnessvalue has been offset by the offset calculating section.

Moreover, in this ultrasonic image processing apparatus, when thethree-dimensional elastic image volume data generated on the basis ofthe reflected echo signals of the plural tomographic planes of theobject is stored in the memory, the offset calculating section may beconfigured to increase or decrease the brightness value of eachcorresponding voxel of the three-dimensional tomographic image volumedata according to the value of elasticity of each voxel of thethree-dimensional elastic image volume data.

An examiner stores the three-dimensional tomographic image volume dataof an object generated by an ultrasonic diagnostic apparatus or the likein information recording media, such as a USB and a CD-ROM, to input itto an ultrasonic image processing apparatus, such as a PC, through animage input section, for example. Alternatively, the three-dimensionaltomographic image volume data of the object may be input through anetwork instead of using the information recording media.

Then, the ultrasonic image processing apparatus executes a step ofincreasing or decreasing the brightness value of each voxel according tothe brightness value of each voxel of the three-dimensional tomographicimage volume data, a step of generating a three-dimensional tomographicimage seen from at least one line-of-sight direction on thetwo-dimensional projection plane on the basis of the three-dimensionaltomographic image volume data in which the brightness value has beenoffset, and a step of displaying the generated three-dimensionaltomographic image as an ultrasonic image processing program.

In addition, when the ultrasonic image processing program includes astep of generating three-dimensional elastic image volume data on thebasis of the reflected echo signals of the plural tomographic planes ofthe object, the brightness value of each corresponding voxel of thethree-dimensional tomographic image volume data may be increased ordecreased according to the value of elasticity of each voxel of thethree-dimensional elastic image volume data in the step of increasing ordecreasing the brightness value of each voxel.

According to this, since the examiner can adjust the amount of increaseor decrease in the brightness value of each voxel of the offsetcalculating section off-line through the input interface of theultrasonic processing apparatus, it is possible to generate athree-dimensional tomographic image in which only tissue with a specificbrightness value is emphasized. Therefore, it is possible to generate athree-dimensional tomographic image with enhanced visibility of desiredspecific tissue by adjusting the amount of increase in the brightnessvalue of the desired specific tissue, adjusting the amount of decreasein the brightness value of tissue other than the desired specifictissue, or adjusting both of them. For example, if the examiner knowsthe brightness value of desired specific tissue, it is possible toenlarge the amount of increase (offset amount) in the brightness valuecorresponding to the vicinity of the brightness value in advance.Moreover, for example, in the case where it is difficult to see desiredspecific tissue since it is hidden behind high-brightness tissue whenviewing the generated three-dimensional tomographic image, it becomesdifficult for the high-brightness tissue as a wall to be reflected onthe three-dimensional tomographic image if the amount of decrease(offset amount) in the brightness value corresponding to the vicinity ofthe high brightness value is set to be large. As a result, it ispossible to improve the visibility of the desired specific tissue.

In addition, since the examiner can adjust the amount of increase ordecrease in the brightness value of each voxel of the offset calculatingsection off-line through the input interface of the ultrasonicprocessing apparatus on the basis of the value of elasticity (stiffnessor softness of tissue) of desired specific tissue, a three-dimensionaltomographic image with enhanced visibility of tissue with a specificvalue of elasticity can be generated. For example, if the examiner knowsthe value of elasticity of desired specific tissue, it is possible toenlarge the amount of increase (offset amount) in the brightness valuecorresponding to the vicinity of the value of elasticity in advance. Onthe other hand, when the examiner wants to observe hard (or soft)tissue, it is possible to find and observe the hard (or soft) tissue ifthe amount of increase (offset amount) in the brightness valuecorresponding to the high (or low) value of elasticity is set high.

REFERENCE SIGNS LIST

1: OBJECT

2: ULTRASONIC PROBE

4: TRANSMISSION SECTION

6: RECEIVING SECTION

8: ULTRASONIC WAVE TRANSMISSION AND RECEPTION CONTROL SECTION

10: PHASING ADDITION SECTION

12: TOMOGRAPHIC IMAGE PROCESSING SECTION

14: TOMOGRAPHIC IMAGE VOLUME DATA GENERATING SECTION

16: OFFSET CALCULATING SECTION

18: TOMOGRAPHIC IMAGE VOLUME RENDERING SECTION

20: TOMOGRAPHIC IMAGE TWO-DIMENSIONAL COORDINATE TRANSFORMATION SECTION

22: IMAGE COMBINING SECTION

24: DISPLAY SECTION

26: CONTROL PANEL

28: CONTROL SECTION

111, 123, 135: BRIGHTNESS-OPACITY MAP

171: RF SIGNAL FRAME DATA SELECTING SECTION

172: DISPLACEMENT MEASURING SECTION

173: ELASTIC INFORMATION CALCULATING SECTION

174: ELASTIC IMAGE PROCESSING SECTION

175: ELASTIC IMAGE VOLUME DATA GENERATING SECTION

176: ELASTIC IMAGE VOLUME RENDERING SECTION

177: ELASTIC IMAGE TWO-DIMENSIONAL COORDINATE TRANSFORMATION SECTION

The invention claimed is:
 1. An ultrasonic diagnostic apparatuscomprising: an ultrasonic probe which transmits or receives anultrasonic wave to or from an object; a tomographic image volume datagenerating section which generates three-dimensional tomographic imagevolume data based on reflected echo signals of a plurality oftomographic planes of the object measured by the ultrasonic probe; atomographic image volume rendering section which generates athree-dimensional tomographic image from at least one line-of-sightdirection on a two-dimensional projection plane based on thethree-dimensional tomographic image volume data; a display section whichdisplays the three-dimensional tomographic image; and an offsetcalculating section which increases or decreases a brightness value ofeach voxel of the three-dimensional tomographic image volume data basedon the brightness value of each voxel, wherein the offset calculatingsection divides a range of the brightness value of each voxel of thethree-dimensional tomographic image data into a plurality of regions,and an amount of increase or decrease in each of the plurality ofregions is set, wherein an amount of increase or decrease in thebrightness value of each voxel is based on the amount increase ordecrease set in each of the plurality of regions, and the amount ofincrease or decrease in the brightness value of each voxel is adjustablevia an input interface, and wherein the tomographic image volumerendering section generates the three-dimensional tomographic imagebased on the three-dimensional tomographic image volume data in whichthe brightness value is offset by the offset calculating section.
 2. Theultrasonic diagnostic apparatus according to claim 1, furthercomprising: an elastic image volume data generating section whichgenerates three-dimensional elastic image volume data based on thereflected echo signals of the plurality of tomographic planes of theobject, wherein the offset calculating section increases or decreasesthe brightness value of each corresponding voxel of thethree-dimensional tomographic image volume data based on the value ofelasticity of each voxel of the three-dimensional elastic image volumedata.
 3. The ultrasonic diagnostic apparatus according to claim 1,wherein the offset calculating section has a plurality of offset tablesin which boundary values for dividing the range of the brightness valueof each voxel of the three-dimensional tomographic image volume datainto the plurality of regions and the amount of increase or decrease inthe brightness value in each of the plurality of divided regions areset, and wherein the brightness value of each voxel of thethree-dimensional tomographic image volume data is increased ordecreased based on the offset table selected from the plurality ofoffset tables via the input interface.
 4. The ultrasonic diagnosticapparatus according to claim 3, wherein the boundary value and theamount of increase or decrease of the offset table are adjustable viathe input interface.
 5. The ultrasonic diagnostic apparatus according toclaim 1, wherein the tomographic image volume rendering section has anopacity table in which transparency/opacity is set according to thebrightness value of each voxel of the three-dimensional tomographicimage volume data, and wherein the three-dimensional tomographic imageis generated based on the brightness value of each voxel on a line ofsight in the at least one line-of-sight direction of thethree-dimensional tomographic image volume data and thetransparency/opacity based on the opacity table.
 6. The ultrasonicdiagnostic apparatus according to claim 1, wherein the tomographic imagevolume rendering section has a brightness-opacity map in whichtransparency/opacity and a color code are set according to thebrightness value of each voxel of the three-dimensional tomographicimage volume data and includes means for generating a two-dimensionaltomographic image by converting a color of each voxel of tomographicimage data of at least one section of the three-dimensional tomographicimage volume data, in which the brightness value is offset, based on thebrightness-opacity map, and wherein the display section displays thethree-dimensional tomographic image, the two-dimensional tomographicimage, and the brightness-opacity map.
 7. The ultrasonic diagnosticapparatus according to claim 2, wherein the offset calculating sectionincreases or decreases the brightness value of each voxel according tothe brightness value of each voxel of the three-dimensional tomographicimage volume data, wherein the tomographic image volume renderingsection increases or decreases the transparency/opacity of each voxelaccording to the value of elasticity of each voxel of thethree-dimensional elastic image volume data, and generates thethree-dimensional tomographic image based on the increased or decreasedbrightness value of each voxel of the three-dimensional tomographicimage volume data and the increased or decreased transparency/opacity.8. The ultrasonic diagnostic apparatus according to claim 2, furthercomprising: an elastic image volume rendering section which generates athree-dimensional elastic image seen from at least one line-of-sightdirection on the two-dimensional projection plane based on thethree-dimensional elastic image volume data; and an image combiningsection which generates a three-dimensional tomographic elastic image byoverlapping the three-dimensional tomographic image generated by thetomographic image volume rendering section and the three-dimensionalelastic image generated by the elastic image volume rendering sectionwith each other, wherein the display section displays thethree-dimensional tomographic elastic image.
 9. A computer programproduct for processing an ultrasonic image, the computer program productcomprising: a computer program; and a non-transitory computer-readablestorage medium having the computer program tangibly embodied thereon,wherein the computer program causes the computer to perform; a step ofgenerating a three-dimensional tomographic image from at least oneline-of-sight direction on a two-dimensional projection plane based onthree-dimensional tomographic image volume data generated based onreflected echo signals of a plurality of tomographic planes of an objectmeasured by an ultrasonic probe; a step of displaying thethree-dimensional tomographic image; and a step of increasing ordecreasing the brightness value of each voxel of the three-dimensionaltomographic image volume data based on the brightness value of eachvoxel: a step of dividing a range of the brightness value of each voxelof the three-dimensional tomographic image data into a plurality ofregions, and setting an amount of increase or decrease in each ofplurality of regions, wherein an of increase or decrease in thebrightness value of each voxel is based on the amount of increase ordecrease set in each of the plurality of regions, and the amount ofincrease or decrease in the brightness value of each voxel in the stepof increasing or decreasing the brightness value of each voxel isadjustable via an input interface, and wherein in the step of generatingthe three-dimensional tomographic image, the three-dimensionaltomographic image is generated based on the three-dimensionaltomographic image volume data in which the brightness value is offset.10. The computer program product according to claim 9, wherein thecomputer program further causes the computer to perform: a step ofgenerating three-dimensional elastic image volume data based on thereflected echo signals of the plurality of tomographic planes of theobject, wherein in the step of increasing or decreasing the brightnessvalue of each voxel, the brightness value of each corresponding voxel ofthe three-dimensional tomographic image volume data is increased ordecreased according to the value of elasticity of each voxel of thethree-dimensional elastic image volume data.
 11. An ultrasonic imagegeneration method comprising: a step of generating a three-dimensionaltomographic image from at least one line-of-sight direction on atwo-dimensional projection plane based on three-dimensional tomographicimage volume data generated based on reflected echo signals of aplurality of tomographic planes of an object measured by an ultrasonicprobe; a step of displaying the three-dimensional tomographic image; anda step of increasing or decreasing a brightness value of each voxel ofthe three-dimensional tomographic image volume data based on thebrightness value of each voxel; a step of dividing a range of thebrightness value of each voxel of the three-dimensional tomographicimage data into a plurality of regions, and setting an amount ofincrease or decrease in each of the plurality of regions, wherein anamount of increase or decrease in the brightness value of each voxel isbased on the amount of increase or decrease set in each of the pluralityof regions, and the amount of increase or decrease in the brightnessvalue of each voxel in the step of increasing or decreasing thebrightness value of each voxel is adjustable via an input interface, andwherein, in the step of generating the three-dimensional tomographicimage, the three-dimensional tomographic image is generated based on thethree-dimensional tomographic image volume data in which the brightnessvalue is offset.
 12. The ultrasonic image generation method according toclaim 11, further comprising: a step of generating three-dimensionalelastic image volume data based on the reflected echo signals of theplurality of tomographic planes of the object, wherein in the step ofincreasing or decreasing the brightness value of each voxel, thebrightness value of each corresponding voxel of the three-dimensionaltomographic image volume data is increased or decreased according to thevalue of elasticity of each voxel of the three-dimensional elastic imagevolume data.
 13. The ultrasonic diagnostic apparatus according to claim2, wherein the offset calculating section has a plurality of offsettables in which boundary values for dividing a range of the value ofelasticity of each voxel of the three-dimensional elastic image volumedata into a plurality of regions and the amount of increase or decreasein the brightness value in each of the plurality of divided regions areset, and wherein the brightness value of each voxel of thethree-dimensional tomographic image volume data is increased ordecreased based on the offset table selected from the plurality ofoffset tables via the input interface.